apt update on Debian appears to be using old sources, how to fix?

I've got a fairly old host that I recently updated to Bookworm (Debian 12). In doing so, I updated the sources list in /etc/apt/sources.list to the following:

deb http://deb.debian.org/debian  bookworm main
deb-src http://deb.debian.org/debian  bookworm main

deb http://deb.debian.org/debian-security/  bookworm-security main
deb-src http://deb.debian.org/debian-security/  bookworm-security main

deb http://deb.debian.org/debian  bookworm-updates main
deb-src http://deb.debian.org/debian  bookworm-updates main

This worked in getting the distro version upgraded. I'm now trying to install openvpn as root, using the command apt update && apt install openvpn (Following the tutorial here: https://std.rocks/vpn_openvpn_bookworm.html) The installation fails, when I try to enable automatic startup of the service using this command (as root):

sed -i 's/#AUTOSTART="all"/AUTOSTART="all"/' /etc/default/openvpn ; systemctl daemon-reload

I get the error: sed: can't read /etc/default/openvpn: No such file or directory In examining the output from the apt install openvpn command, I see multiple references to old distros. My assumption is that there is some other place where sources need to be updated, but I'm not sure about that. Is my assumption correct that there are lingering old sources that I need to update? Or have I misread the output and need to look elsewhere?

@gemini:~# apt update && apt install openvpn
Hit: 1 http://deb.debian.org/debian  bookworm InRelease
Hit:2 http://deb.debian.org/debian-security  bookworm-security InRelease Hit: 3 http://deb.debian.org/debian  bookworm-updates InRelease
Get:4 https://deb.nodesource.com/node_6.x  jessie InRelease [4,607 B] Ign:5 http://ppa.launchpad.net/certbot/certbot/ubuntu  jessie InRelease Ign:6 http://nginx.org/packages/debian  codename InRelease
Err:7 http://nginx.org/packages/debian  codename Release
404
Not Found [IP: 2a05: d014:5c0:2601::6 80]
Err:8 http://ppa.launchpad.net/certbot/certbot/ubuntu  jessie Release
404 Not Found [IP: 2620:2d:4000:1::81 80]
Get:9 http://ppa.launchpad.net/maxmind/ppa/ubuntu  eoan InRelease [15.9 kB]
Get:10 http://ppa.launchpad.net/ondrej/nginx/ubuntu  eoan InRelease [21.5 KB]
Err:9 http://ppa.launchpad.net/maxmind/ppa/ubuntu  eoan InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY DE1997DCD Err:10 http://ppa.launchpad.net/ondrej/nginx/ubuntu  eoan InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 71DAEAAB4 Reading package lists... Done
E: The repository 'http://nginx.org/packages/debian  codename Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure (8) manpage for repository creation and user configuration details.
E: The repository 'http://ppa.launchpad.net/certbot/certbot/ubuntu  jessie Release' does not have a Release f
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure (8) manpage for repository creation and user configuration details.
W: https://deb.nodesource.com/node_6.x/dists/jessie/InRelease : Key is stored in legacy trusted.gpg keyring ( ion in apt-key (8) for details.
W: GPG error: http://ppa.launchpad.net/maxmind/ppa/ubuntu  eoan InRelease: The following signatures couldn't able: NO_PUBKEY DE 1997DCDE742AFA
E: The repository 'http://ppa.launchpad.net/maxmind/ppa/ubuntu  eoan InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure (8) manpage for repository creation and user configuration details.
W: GPG error: http://ppa.launchpad.net/ondrej/nginx/ubuntu  eoan InRelease: The following signatures couldn't lable: NO_PUBKEY 71DAEAAB4AD4CAB6 NO_PUBKEY 4F4EA0AAE 5267A6C
E: The repository 'http://ppa.launchpad.net/ondrej/nginx/ubuntu  eoan InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure (8) manpage for repository creation and user configuration details.